Field of the Invention
The present disclosure generally relates to an apparatus for semiconductor processing. More specifically, the present disclosure relates to apparatus for controlling air flow in an epitaxy chamber.
Description of the Related Art
Epitaxy is a process commonly used in semiconductor processing to fabricate high quality materials with uniform electrical properties for semiconductor devices. In a typical epitaxy chamber, process gasses flow across a substrate in a direction parallel to the substrate to form a film on the substrate. The process gasses typically flow from one side of the chamber to the other side, where exhaust gases are removed.
A prior implementation of a cone 30 for controlling air flow to control deposition on an upper dome of an epitaxy chamber is shown in FIG. 1 (Prior Art) for comparison to FIG. 2 below. The cone 30 shown in FIG. 1 has a cylindrical shaped portion and a tapered lower portion 31. The lower portion is tapered to control air flow and produce a more uniform substrate temperature. A single slit 32 extends from a top of the cone 30 to a bottom of the cone 30. When placed in an epitaxy chamber, the cone 30 is positioned above an upper dome and the single slit 32 of the cone 30 is placed beneath a pyrometer to allow passage of infrared waves through the single slit 32 of the cone 30.
The arrows in FIG. 1 illustrate air flow through the cone 30 when the air enters the top of the cone 30. Air travels down through the cone 30 and exits to the bottom of the cone 30, while some of the air introduced into the cone 30 exits to the side of the cone 30 through the single slit 32.
Deposits formed on an upper dome when using the cone 30 impact the performance of the chamber during processing. For example, any coating on the upper dome may block light irradiation from reaching a portion of the substrate during processing, compromising the uniformity of the film formed on the substrate. Coatings on the upper dome can also cause slip dislocations across the surface of the substrate. Coatings may form on the upper dome if the upper dome has non-uniform temperatures during processing. The coatings often form in areas of extreme high and low temperatures on the upper dome at the exhaust side of the chamber.
Thus, a need exists for techniques to reduce or eliminate coatings formed on the upper dome above the substrate during processing in a high growth rate epitaxy chamber.